U.S. patent application number 12/601662 was filed with the patent office on 2010-10-07 for deep anodization.
Invention is credited to Lev Furer, Uri Mirsky, Shimon Neftin.
Application Number | 20100255274 12/601662 |
Document ID | / |
Family ID | 40032269 |
Filed Date | 2010-10-07 |
United States Patent
Application |
20100255274 |
Kind Code |
A1 |
Mirsky; Uri ; et
al. |
October 7, 2010 |
DEEP ANODIZATION
Abstract
A method of anodizing comprising anodizing at least a portion of
a valve metal base to a depth of at least 200 .mu.m.
Inventors: |
Mirsky; Uri; (Nofit, IL)
; Neftin; Shimon; (Kiryat Shmonah, IL) ; Furer;
Lev; (Haifa, IL) |
Correspondence
Address: |
BROWDY AND NEIMARK, P.L.L.C.;624 NINTH STREET, NW
SUITE 300
WASHINGTON
DC
20001-5303
US
|
Family ID: |
40032269 |
Appl. No.: |
12/601662 |
Filed: |
May 25, 2008 |
PCT Filed: |
May 25, 2008 |
PCT NO: |
PCT/IL08/00705 |
371 Date: |
June 1, 2010 |
Current U.S.
Class: |
428/209 ;
205/118 |
Current CPC
Class: |
C25D 11/16 20130101;
Y10T 428/24917 20150115; C25D 11/04 20130101 |
Class at
Publication: |
428/209 ;
205/118 |
International
Class: |
B32B 15/20 20060101
B32B015/20; C25D 9/06 20060101 C25D009/06 |
Claims
1.-42. (canceled)
43. A method of anodizing comprising: anodizing at least a portion
of a valve metal base to a depth of at least 200 .mu.m.
44. The method of claim 43, further comprising creating, prior to
anodization, an indentation on at least a portion of at least one
surface of the base.
45. The method of claim 44, wherein the anodization is performed on
at least a portion of the indentation.
46. The method of claim 44, comprising creating the indentation on
at least a portion of two surfaces of the base.
47. The method of claim 46, wherein the anodization is performed on
at least a portion of the indentation.
48. The method of claim 44, wherein the indentation comprises a
blind hole.
49. The method of claim 44, wherein the indentation comprises a
groove.
50. The method of claim 44, wherein the indentation comprises a
recess.
51. The method of claim 44, wherein the indentation comprises a
cavity.
52. The method of claim 44, wherein the indentation comprises a
channel.
53. The method of claim 44, wherein the indentation comprises an
etching.
54. The method of claim 43, wherein the base comprises
aluminum.
55. The method of claim 43, wherein anodizing comprises growing
aluminum oxide(ALOX).
56. The method of claim 55, further comprising overlapping the ALOX
grown from at least two indentations on at least a portion of at
least one surface of the base.
57. The method of claim 55, further comprising overlapping the ALOX
grown from at least two indentations on at least a portion of two
surfaces of the base.
58. The method of claim 43, wherein the base is a part of an ALOX
substrate.
59. The method of claim 58, further comprising creating an
essentially vertical isolating structure in the substrate.
60. A substrate comprising: a valve metal base comprising at least
a portion anodized to a depth of minimum 200 .mu.m.
61. The substrate of claim 60, wherein the valve metal base
comprises aluminum.
62. The substrate of claim 60, wherein the anodized portion
comprises ALOX.
63. The substrate of claim 60, further comprising an essentially
vertical isolating structures formed by anodization.
Description
FIELD
[0001] The invention relates to anodized substrates.
BACKGROUND
[0002] Anodizing, or controlled oxidation, is an electrochemical
process typically used to build a thickness and a density of a
naturally forming oxide layer on a surface of a metal. For
convenience hereinafter, a metal on which an oxide layer is formed,
either naturally or through anodizing, will be referred to as a
"substrate". By increasing the thickness and density of the oxide
layer anodizing generally provides for improved corrosion and wear
resistance in the substrate. Additionally, it provides for
substantially better adhesion of paints, and/or epoxies, and/or
other protective/decorative coating materials onto the base.
Optionally, it provides for electrical isolation.
[0003] Aluminum and aluminum alloys are examples of types of metals
on which a protective oxide layer naturally forms along the surface
when the surface is exposed to the atmosphere. The oxide layer is
generally adapted to moderately protect the metal from corrosion.
For convenience hereinafter, the metal, prior to the formation of
an oxide layer shall be referred to as "base". In order to have
increased protection over that provided by the naturally formed
oxide layer, the base generally undergoes anodizing. Typically, for
aluminum and aluminum alloys, anodizing is performed by submerging
the base in a solution soluble to aluminum oxide (Alox), such as
oxalic acid, phosphoric acid, sulphuric acid, chromic acid or any
other appropriate material. A direct current is passed through the
solution, the base acting as an anode, or positive electrode and an
electrode inserted in the solution acting as a negative electrode,
or cathode. As a result of the current, hydrogen is released by the
solution at the cathode, and oxygen is released at the surface of
the base acting as the anode. The released oxygen produces a
buildup of the Alox layers on the surface of the base. The
dimensions of the Alox layers are typically controlled during an
anodization process by controlling duration of the process, current
density, voltage between the electrodes, temperature of the
solution, or any combination thereof.
[0004] Numerous applications require the substrates to have
relatively large heat transfer characteristics. Examples of such
applications may comprise devices used in high temperature
environments such as may be found, for example, in high performance
light engines, ovens for component fabrication, high power laser
equipment and high power RF device and/or equipment. Other examples
may comprise devices used in lower temperature environments such as
may be found in high power small volume, for example .about.100
W/cm.sup.2 or more, devices and/or equipment, mobile phones,
portable computers, and plasma displays.
[0005] ALOX.TM. substrate technology is a unique multilayer
substrate technology developed for microelectronics packaging
applications. The process is simple and low cost, and contains a
low number of process steps. The ALOX.TM. substrate technology
serves as a wide technology platform, and can be implemented in
various electronics packaging applications such as for RF, SiP, 3-D
memory stacks, MEMS and high power modules and components. ALOX.TM.
technology is described in U.S. Pat. No. 5,661,341 "Method of
Manufacturing a Composite Structure for Use in Electronic Devices
and Structure, Manufactured by Said Method"; U.S. Pat. No.
6,448,510 "Substrate for Electronic Packaging, Pin Jig Fixture";
U.S. Pat. No. 6,670,704 "Device for Electronic Packaging, Pin Jig
Fixture"; International Patent Publication No. WO 00/31797,
International Patent Publication No. WO 04/049424, and U.S. Patent
Application Pub No. 2007/0080360 "Microelectronic Interconnect
Substrate and Packaging Techniques", all of which are incorporated
herein by reference in their entirety.
[0006] A starting material in an ALOX.TM. process is a conductive
aluminum sheet. A first step in the process is masking the top and
bottom of the sheet using conventional lithography techniques (for
example, photoresist). Via structures, comprising solid aluminum,
are formed using anodization of the sheet through the whole
thickness of the sheet. The exposed areas are converted into
aluminum oxide which is ceramic in nature and a highly insulating
dielectric material. The protected unexposed areas remain as
aluminum elements and form the connecting vias.
[0007] In its simplest form, an ALOX.TM. interconnect substrate is
formed by electrochemical anodic oxidation of selected portions of
an initially conductive valve metal (for example, aluminum)
substrate resulting in areas (regions) of conductive (starting)
material which are geometrically defined and isolated from one
another by areas (regions) of anodized (non-conductive, such as
aluminum oxide, or alumina) isolation structures. "Vertical"
isolation structures extend into the substrate, including
completely through the substrate. "Horizontal" isolation structures
extend laterally across the substrate, generally just within a
surface thereof Anodizing from one or both sides of the substrate
can be performed to arrive at complex interconnect structures.
[0008] In a more complex form (such as disclosed in U.S. Pat. No.
6,670,704), a multilayer low cost ceramic board is formed using
this process. A complete "three metal layer" core contains an
internal aluminum layer, top and bottom patterned copper layers
with through vias and blind vias incorporated in the structure.
GLOSSARY
[0009] Unless otherwise noted, or as may be evident from the
context of their usage, any terms, abbreviations, acronyms or
scientific symbols and notations used herein are to be given their
ordinary meaning in the technical discipline to which the
disclosure most nearly pertains. The following terms, abbreviations
and acronyms may be used throughout the descriptions presented
herein and should generally be given the following meaning unless
contradicted or elaborated upon by other descriptions set forth
herein. Some of the terms set forth below may be registered
trademarks (.RTM.). [0010] anodization, one-sided An anodization
process applied to a surface on one side of a metal sheet (or
substrate). An example of such a process may include the use of
ALOX.TM. substrate technology. [0011] anodization, two-sided An
anodization process applied to a surface on both sides of a metal
sheet (or substrate). An example of such a process may include the
use of ALOX.TM. substrate technology. [0012] ALOX.TM. A substrate
technology (proprietary to Micro Components Ltd. of Ramat-Gabriel,
Israel) wherein the substrate is metal based, made of a combination
of aluminum metal and aluminum oxide based dielectric material
forming a multi layer interconnect substrate, typically in a BGA
format. [0013] Aluminum Aluminium, or aluminum (Symbol Al). [0014]
Aluminium oxide An amphoteric oxide of aluminium (for example,
having the chemical formula Al.sub.2O.sub.3), also commonly
referred to as alumina. [0015] array A set of elements (usually
referring to leads or balls in the context of semiconductor
assembly) arranged in rows and columns. [0016] assembly The process
of putting a semiconductor device or integrated circuit in a
package of one form or another; it usually consists of a series of
packaging steps that include: die preparation, die attach, wire
bonding, encapsulation or sealing, deflash, lead trimming/forming,
and lead finish. [0017] ball bond A bond that looks like a ball
(generally spherical). [0018] ball grid array (BGA) A surface-mount
package that utilizes an array of metal spheres or balls as the
means of providing external electrical interconnection, as opposed
to the pin-grid array (PGA) which uses an array of leads for that
purpose. [0019] CBGA Short for `Ceramic Ball Grid Array`. [0020]
chip A portion of a semiconductor wafer, typically containing an
entire circuit which has not yet been packaged [0021] chip-scale
package (CSP) Any package whose dimensions do not exceed the die's
dimensions by 20%. [0022] die 1. A single chip from a wafer; 2. A
small block of semiconductor material containing device circuitry.
[0023] die attach The assembly process step wherein the die is
mounted on the support structure of the package, for example, the
leadframe, die pad, cavity, or substrate. [0024] die Used
synonymously with "chip". Plural, "dies" or "dice". [0025] heat
sink Devices used to absorb or transfer (conduct) heat away from
heat sensitive devices or electronic components. [0026] IC or ICC
Short for Integrated Circuit, or Integrated Circuit Chip. [0027]
Interconnect Substrate As used herein, an interconnect substrate is
a typically flat substrate used to connect electronic components
with one another and having patterns of conductive traces in at
least one layer for effecting routing of signals (and power) from
one electronic component to another, or to the outside world.
Typically, an interconnect substrate has many metallization layers
with the conductive traces, and vias connect selected traces from
one layer to selected traces of another layer. [0028] interposer An
intermediate layer or structure that provides electrical connection
between the die and the package. [0029] leadframe A metal frame
used as skeleton support to provide electrical connections to a
chip in many package types. [0030] Light Emitting Diode (LED) A
junction diode which give off light (and also generates some heat)
when energized. [0031] mask Broadly speaking, a mask is any
material forming a pattern for a subsequent process to selectively
affect/alter certain areas of a semiconductor substrate, and not
others. Photoresist is a commonly-used masking material which is
applied to the substrate, then washed off (stripped) after the
desired process is completed. [0032] MCM Short for multi-chip
module. In accordance with a basic definition and classification,
given in "Thin film multichip modules" by George Messner, Iwona
Turlik, John W. Balde and Philip E. Garrou, edited by the
International Society for Hybrid Microelectronics, 1992, the
multichip module is a device, which provides the interconnections
for several chips that are subsequently protected by a coating or
an enclosure. In accordance with different approaches and
fabrication techniques, the MCMs known today can be divided into 3
main groups: [0033] MCM-C Short for `Multi-Chip Module-Ceramic`.
MCM-Cs are multichip modules which use sinterable metals to form
the conductive patterns of signal and power layers, which are
applied onto a substrate made of ceramic or glass-ceramic material.
[0034] MCM-L Short for `Multi-Chip Module-Laminate`. MCM-Ls are
multichip modules which use laminate structures and employ printed
circuit technologies to form a pattern of signal and power layers,
which are applied onto layers made of organic insulating material.
[0035] MCM-D Short for `Multi-Chip Module-Dense`. MCM-Ds are
multichip modules on which layers of metal and insulator are
usually formed by the deposition of thin film onto a rigid support
structure usually made of silicon, ceramic, or metal. [0036] MEMS
Short for Micro Electro Mechanical Systems. MEMS micromachined in
silicon, typically integrated with electronic microcircuits,
generally fall into two categories of micro sensors and micro
actuators; depending on application operation based on
electrostriction, or electromagnetic, thermo elastic,
piezoelectric, or piezoresistive effect. [0037] microelectronics
The branch of electronics that deals with miniature (often
microscopic) electronic components. [0038] molding The assembly
process step wherein the devices are encapsulated in plastic; also
referred to as `encapsulation`. [0039] package A container, case,
or enclosure for protecting a (typically solid-state) electronic
device from the environment and providing connections for
integrating a packaged device with other electronic components.
[0040] photoresist (resist) Photoresist (PR) is a photo-sensitive
material used in photolithography to transfer a pattern from a mask
onto a wafer. Typically, a liquid deposited on the surface of the
wafer as a thin film then solidified by low temperature anneal.
Exposure to light (irradiation) changes the properties of the
photoresist, specifically its solubility. "Negative" resist is
initially soluble, but becomes insoluble after irradiation.
"Positive" resist is initially insoluble, but becomes soluble after
irradiation. Photoresist is often used as an etch mask. In the
context of the present disclosure, photoresist may be used as an
oxidation mask. [0041] PWB Short for printed wiring board. Also
referred to as printed circuit board (PCB). [0042] RF Short for
`Radio Frequency`. RF refers to that portion of the electromagnetic
spectrum in which electromagnetic waves can be generated by
alternating current fed to an antenna. [0043] semiconductors 1. Any
of various solid crystalline substances, such as germanium or
silicon, having electrical conductivity greater than insulators but
less than good conductors, and used especially as a base material
for computer chips and other electronic devices. 2. An integrated
circuit or other electronic component containing a semiconductor as
a base material. [0044] SIP Short for `System-in-a-Package`--a
package that contains several chips and components that comprise a
completely functional stand-alone electronic system (also acronym
for `Single-in-Line Package`--a through-hole package whose leads
are aligned in just a single row, but that definition is not used
in the description herein). [0045] SMD Short for `Surface-Mount
Device`. [0046] SMT Short for `Surface-Mount Technology`. [0047]
substrate 1. The base material of the support structure of an IC;
2. The surface where the die or other components are mounted in
electronic packaging; 3. The semiconductor block upon which the
integrated circuit is built. [0048] surface-mount A phrase used to
denote that a package is mounted directly on the top surface of the
board, as opposed to `through-hole`, which refers to a package
whose leads need to go through holes in the board in order to get
them soldered on the other side of the board. [0049] valve metal A
metal, such as aluminum, which is normally electrically conductive,
but which can be converted such as by oxidation to both a
non-conductor (insulator) and chemical resistance material. Valve
metals include aluminum (Al, including Al 5052, Al 5083, Al 5086,
Al 1100, Al 1145, and the like), titanium, tantalum, also niobium,
europium. [0050] via A metallized or plated-through hole, in an
insulating layer, for example, a substrate, chip or a printed
circuit board which forms a conduction path itself and is not
designed to have a wire or lead inserted therethrough. Vias can be
either straight through (from front to back surface of the
substrate) or "blind". A blind via is a via that extends from one
surface of a substrate to within the substrate, but not through the
substrate. [0051] wire bond Attachment of a tiny wire, as by thermo
compression bonding and/or ultrasound, to a bonding pad on a
semiconductor chip substrate bond finger. [0052] wirebonding An
assembly process or step that connects wires between the die and
the bonding sites of the package (for example, the lead fingers of
the leadframe or the bonding posts of the package).
SUMMARY
[0053] An aspect of some embodiments of the invention relates to
providing a method for deep anodization of at least a portion of a
thick substrate comprising a thick valve metal base (minimum
thickness 200 .mu.m), wherein the anodization reaches a depth of at
least 200 .mu.m into the base from a surface of the base exposed to
an anodization process. By using the disclosed method, for example,
anodization may be used for via forming in a thick substrate of
thickness at least 0.4 mm. Via forming in a thick substrate
provides for substantially high breakdown voltage, and for high
power dissipation in micromechanical, optical, thermal applications
For convenience hereinafter, the method may be referred to as `deep
anodization`. A method for deep anodization is described in
Provisional Patent Application No. 60/924656 filed 24 May 2007,
which is incorporated herein by reference in its entirety.
[0054] According to an aspect of some embodiments of the invention,
the method comprises, prior to anodization, partially reducing a
thickness of one or more portions of the base which are to undergo
deep anodization. For convenience hereinafter, "partially reducing
the thickness of a portion" may be used interchangeably with
"thickness reduction". Thickness reduction may include forming
indentations such as, for example, recesses, openings (for example,
blind holes), cavities, grooves, etchings, or any combination
thereof, on the surface of the base comprising the portion. In an
embodiment of the invention, the method comprises one-sided deep
porous anodization and includes thickness reduction and anodization
from one side of the base. Optionally, the method comprises
two-sided deep porous anodization and includes thickness reduction
and anodization from two sides of the base. Thickness reduction may
be performed by using methods known in the art, such as, for
example, chemical or electrochemical or dry etching through an
opening in a mask; jet spraying of an etchant; or through
mechanical means such as milling, stamping, electro erosion,
ultrasound cutting, laser cutting, or any combination thereof
[0055] In some embodiments of the invention, deep anodization may
be used to create vertical isolated structures in a thick ALOX.TM.
substrate. The thick ALOX.TM. substrate may then be adapted for
packaging high power electronics, such as, for example, high power
LEDs, high power RF, and/or other types of high power modules.
[0056] There is provided, in accordance with an embodiment of the
invention, a method of anodizing comprising anodizing at least a
portion of a valve metal base to a depth of at least 200 .mu.m. The
method further comprises creating, prior to anodization, an
indentation on at least a portion of at least one surface of the
base. Optionally, the anodization is performed on at least a
portion of the indentation.
[0057] In some embodiments of the invention, the method comprises
creating the indentation on at least a portion of two surfaces of
the base. Optionally, the anodization is performed on at least a
portion of the indentation.
[0058] In some embodiments of the invention, the indentation
comprises a blind hole. Optionally, the indentation comprises a
groove. Optionally, the indentation comprises a recess.
Additionally or alternatively, the indentation comprises a cavity.
Optionally, the indentation comprises a channel. Optionally, the
indentation comprises an etching.
[0059] In some embodiments of the invention, the base comprises
aluminum. Optionally, anodizing comprises growing aluminum oxide
(alox). Optionally, the method further comprises overlapping the
alox grown from at least two indentations on at least a portion of
at least one surface of the base. Additionally or alternatively,
the method further comprises overlapping the alox grown from at
least two indentations on at least a portion of two surfaces of the
base.
[0060] In some embodiments of the invention, the base is a part of
an ALOX.TM. substrate. Optionally, the method further comprises
creating an essentially vertical isolating structure in the
substrate.
[0061] There is provided, in accordance with an embodiment of the
invention, a substrate comprising a valve metal base comprising at
least a portion anodized to a depth of minimum 200 .mu.m.
Optionally, the valve metal base comprises aluminum. Optionally,
the anodized portion comprises alox.
[0062] In some embodiments of the invention, the substrate further
comprises an ALOX.TM. substrate. Optionally, the substrate
comprises an essentially vertical isolating structure formed by
anodization. Optionally, the substrate further comprises an
aluminum via having a minimum thickness of 200 .mu.m.
[0063] There is provided, in accordance with an embodiment of the
invention, a substrate comprising a valve metal base comprising at
least a portion anodized to a depth of minimum 200 .mu.m wherein
the portion was produced by creating, prior to anodization, an
indentation on at least a portion of at least one surface of the
base. The substrate further comprises an indentation on at least a
portion of two surfaces of the base. Optionally, at least a portion
of the indentation is anodized. Optionally, the indentation
comprises a blind hole. Optionally, the indentation comprises a
groove. Optionally, the indentation comprises a recess.
Additionally or alternatively, the indentation comprises a cavity.
Optionally, the indentation comprises a channel. Optionally, the
indentation comprises an etching. Optionally, the base comprises
aluminum. Optionally, anodizing comprises growing aluminum oxide
(alox). Additionally or alternatively, the alox grown is from at
least two indentations on at least a portion of at least one
surface of the base overlap. Optionally, the alox is grown from at
least two indentations on at least a portion of two surfaces of the
base. Optionally, the base is a part of an ALOXTM substrate.
[0064] There is provided, in accordance with an embodiment of the
invention, an interconnect substrate comprising a valve metal base
comprising at least a portion anodized to a depth of minimum 200
.mu.m, wherein the portion was produced by creating, prior to
anodization, an indentation on at least a portion of at least one
surface of the base.
[0065] There is provided, in accordance with an embodiment of the
invention, an electronic device comprising a substrate comprising a
valve metal base, the valve metal base comprising at least a
portion anodized to a depth of minimum 200 .mu.m, wherein the
portion was produced by creating, prior to anodization, an
indentation on at least a portion of at least one surface of the
base.
[0066] There is provided, in accordance with an embodiment of the
invention, an electronic device comprising an interconnect
substrate comprising a valve metal base, the valve metal base
comprising at least a portion anodized to a depth of minimum 200
.mu.m wherein the portion was produced by creating, prior to
anodization, an indentation on at least a portion of at least one
surface of the base.
BRIEF DESCRIPTION OF FIGURES
[0067] Examples illustrative of embodiments of the invention are
described below with reference to figures attached hereto. In the
figures, identical structures, elements or parts that appear in
more than one figure are generally labeled with a same numeral in
all the figures in which they appear. Dimensions of components and
features shown in the figures are generally chosen for convenience
and clarity of presentation and are not necessarily shown to scale.
The figures are listed below.
[0068] FIG. 1 A schematically illustrates an isometric view of an
exemplary substrate in an implementation of the method, prior to
anodization and comprising indentations for thickness reduction, in
accordance with an embodiment of the invention;
[0069] FIG. 1B schematically illustrates a cross-sectional view A-A
of the substrate shown in FIG. 1A, in accordance with an embodiment
of the invention;
[0070] FIG. 1C schematically illustrates a cross-sectional view B-B
of the substrate shown in FIG. 1A, in accordance with an embodiment
of the invention;
[0071] FIG. 2A schematically illustrates an isometric view of the
substrate shown in FIG. 1A following anodization, in accordance
with an embodiment of the invention;
[0072] FIG. 2B schematically illustrates a cross-sectional view A-A
of the substrate shown in FIG. 2A, in accordance with an embodiment
of the invention;
[0073] FIG. 2C schematically illustrates a cross-sectional view B-B
of the substrate shown in FIG. 2A, in accordance with an embodiment
of the invention;
[0074] FIG. 2D schematically illustrates an isometric view of an
exemplary substrate in an implementation of the method, following
anodization, in accordance with an embodiment of the invention;
[0075] FIG. 2E schematically illustrates a cross-sectional view C-C
of the substrate shown in FIG. 2D, in accordance with an embodiment
of the invention;
[0076] FIG. 2F schematically illustrates a cross-sectional view D-D
of the substrate shown in FIG. 2D, in accordance with an embodiment
of the invention;
[0077] FIGS. 3A-3E schematically illustrate several non-limiting,
exemplary plan views of a alox configurations on a portion of a
surface of a substrate following implementation of the method,
marked A-H, in accordance with some embodiments of the
invention;
[0078] FIGS. 4A-4E and 4A'-4E' schematically illustrate several
non-limiting, exemplary cross-sectional views of alox
configurations on a portion of a substrate prior to anodization;
and the same cross-sectional views of the portion following
anodization, respectively, in accordance with some embodiments of
the invention;
[0079] FIG. 5 schematically illustrates an exemplary thick ALOX.TM.
substrate following deep anodization and comprising vertical
isolated structures, in accordance with some embodiments of the
invention; and
[0080] FIG. 6 illustrates a flow diagram of an exemplary method of
performing deep anodization, in accordance with an embodiment of
the invention.
DETAILED DESCRIPTION
[0081] Reference is made to FIG. 1A, which schematically
illustrates a partial isometric view of an exemplary substrate 100
in an implementation of the method, prior to anodization, and
comprising indentations, such as for example, blind holes 102, for
thickness reduction in a valve metal base 101; to FIG. 1B which
schematically illustrates a cross-sectional view A-A of substrate
100; and to FIG. 1C which schematically illustrates a
cross-sectional view B-B of substrate 100, all in accordance with
an embodiment of the invention. Base 101 may be fabricated from
valve metals, such as, for example, aluminum.
[0082] In accordance with an embodiment of the invention, blind
holes 102 are created on a portion of a surface on one side of base
101 as a step of a one-sided deep anodization process. Holes 102
are of diameter d and depth h, and are spaced a distance l from one
another, the dimensions d, h, and/or l selected so as to satisfy a
predetermined criteria for area and depth to be anodized in base
101. In selecting d, h, and l, consideration is given to a type of
anodization process used and a growth amount of aluminum oxide
(alox) into metal and out of metal. For example, when using a
porous anodization process, such as, for example, that used to
create an ALOX.TM. substrate, alox growth into aluminum may be
approximately 70%, while out of the aluminum, growth may be
approximately 30%. Optionally, holes 102 may include shapes other
than circular, for example, elliptical, triangular, rectangular, or
any other polygonal shape, or any combination thereof. Additionally
or alternatively, holes 102 may be connected to one another to form
grooves, channels, and the like. Holes 102 may be created by
methods known in the art, such as, for example, chemical or
electrochemical or dry etching through an opening in mask; jet
spraying of an etchant; or through mechanical means such as
milling, stamping, electro erosion, ultrasound cutting, laser
cutting, or any combination thereof.
[0083] Reference is made to FIG. 2A, which schematically
illustrates a partial isometric view of exemplary substrate 100
shown in FIG. 1A following one-sided deep anodization; to FIG. 2B
which schematically illustrates a cross-sectional view A-A of
substrate 100 shown in FIG. 2A; and to FIG. 2C which schematically
illustrates a cross-sectional view B-B of substrate 100 shown in
FIG. 2A, all in accordance with an embodiment of the invention.
[0084] In accordance with an embodiment of the invention,
dimensions d, h, and l are selected so that a growth of alox 103
into base 101, through each hole 102, substantially reaches a
predetermined depth h' exceeding 204m, and overlaps with that of
the adjacent hole a distance l away. Furthermore, dimension h in
hole 102 may be selected such that growth of alox 103 inside the
hole substantially fills the hole to a height substantially in the
same plane as the side of base 101 in which the hole was created.
For example, in the creation of a thick ALOX.TM. substrate (alox
growth into aluminum is approximately 70%, while out of the
aluminum, growth is approximately 30%), selecting the depth of a
hole to be approximately 30% of the total thickness of the alox
will result in a substantially completely filled hole during the
porous anodization process, a top of the hole essentially lying in
a same plane as a side of a base in which the hole was created. The
result is the creation of a strip of alox 103 which extends a depth
h' into base 101, and covers an approximate area on a portion of
base 101 of width d' and length L. Each blind hole 102 is fully
filled.
[0085] In another embodiment of the invention, dimension h in hole
102 may be selected such that the hole is not completely filled.
Reference is made to FIG. 2D which schematically illustrates a
partial isometric view of an exemplary substrate 100' following
one-sided deep anodization; to FIG. 2E which schematically
illustrates a cross-sectional view C-C of substrate 100' shown in
FIG. 2D; and to FIG. 2F which schematically illustrates a
cross-sectional view D-D of substrate 100' shown in FIG. 2D, all in
accordance with another embodiment of the invention. Reference is
also made to FIG. 1. Exemplary substrate 100', prior to
anodization, may be the same or substantially similar to that shown
in FIG. 1 at 100.
[0086] In accordance with another embodiment of the invention,
dimensions d, h, and l in base 101 are selected so that a growth of
alox 103' into base 101' substantially reaches a predetermined
depth h' exceeding 200 .mu.m and overlaps with alox 103' growth
from an adjacent hole 102 a distance l away (holes 102 are shown in
FIG. 1). This results in the creation of a strip of alox 103' which
extends a depth h' into base 101', and covers an approximate area
on a portion of base 101' of width d' and length L. Each blind hole
102 in base 101 has been reduced to a small hole 104' in base 101'
during the anodization process due to the growth of alox 103'
outwards from the metal.
[0087] Reference is made to FIGS. 3A-3H which schematically
illustrate several non-limiting, exemplary plan views of alox
configurations on a portion of a surface of a substrate following
implementation of the method, in accordance with some embodiments
of the disclosure. The method may comprise one-sided deep
anodization, or optionally, two-sided deep anodization. Thickness
reduction by creating indentations may be performed by using
methods known in the art, such as, for example, chemical or
electrochemical or dry etching through an opening in a mask; jet
spraying of an etchant; or through mechanical means such as
milling, stamping, electro erosion, ultrasound cutting, laser
cutting, or any combination thereof. Anodization may be performed
using methods known in the art, for example, porous
anodization.
[0088] FIG. 3A shows a substrate 300 including a section of an
aluminum base 301 with one, essentially circular area of alox 303,
following a deep anodization process using a blind hole for
thickness reduction. The blind hole may be the same or
substantially similar to that shown in FIG. 1 at 102, and has been
filled during the anodization process due to the growth of alox 303
outwards from the metal. Substrate 300, including aluminum base 301
and alox 303, may be the same or substantially similar to that
shown in FIGS. 2A-2C at 100, 101, and 103.
[0089] FIG. 3B shows a substrate 310 including a section of an
aluminum base 311 with three, essentially circular areas of grown
alox 313, following a deep anodization process using blind holes
for thickness reduction. The blind hole may be the same or
substantially similar to that shown in FIG. 1 at 102. Each circular
area of alox 313 was created from a blind hole, the distance
between the holes selected such that the grown circular areas are
physically separated from one another by portions of aluminum base
311. Each blind hole has been filled during the anodization process
due to the growth of alox 313 outwards from the metal. Substrate
310, including aluminum base 311 and alox 313, may be the same or
substantially similar to that shown in FIGS. 2A-2C at 100, 101, 102
and 103.
[0090] FIG. 3C shows a substrate 320 including a section of an
aluminum base 321 with a relatively large area of grown alox 323,
following a deep anodization process using blind holes for
thickness reduction. The blind holes may be the same or
substantially similar to that shown in FIG. 1 at 102. The area of
grown alox 323 was created from two rows of blind holes, the
distance between the holes selected such that the alox grown from
each hole overlaps with the alox grown in an adjacent blind hole in
the same row, and with an adjacent blind hole in the adjacent row.
Each blind hole has been filled during the anodization process due
to the growth of alox 323 outwards from the metal. Substrate 320,
including aluminum base 321 and alox 323, may be the same or
substantially similar to that shown in FIGS. 2A-2C at 100, 101, 102
and 103.
[0091] FIG. 3D shows a substrate 330 including a section of an
aluminum base 331 with two strips of grown alox 333, following a
deep anodization process using blind holes for thickness reduction.
The blind holes may be the same or substantially similar to that
shown in FIG. 1 at 102. Each strip of grown alox 333 was created
from a row of blind holes, the distance between the holes selected
such that the alox grown from each hole overlaps with the grown
alox of an adjacent blind hole in the same row. The two rows of
blind holes were separated by a distance such that two strips of
grown alox 333 are separated by a portion of aluminum base 331.
Each blind hole has been filled during the anodization process due
to the growth of alox 333 outwards from the metal. Substrate 330,
including aluminum base 331 and alox 333, may be the same or
substantially similar to that shown in FIGS. 2A-2C at 100, 101,
102, and 103.
[0092] FIG. 3E shows a substrate 340 including a section of an
aluminum base 341 with a relatively large strip of grown alox 343,
following a deep anodization process using a groove for thickness
reduction. Optionally, the groove may be a channel, a recess, or
the like. The groove has been filled during the anodization process
due to the growth of alox 343 outwards from the metal. Substrate
340, including aluminum base 341 and alox 343 may be the same or
substantially similar to that shown in FIGS. 2A-2C at 200, 201, and
203.
[0093] FIG. 3F shows a substrate 350 including a section of an
aluminum base 351 with a relatively large area of grown alox 353,
following a deep anodization process using three grooves for
thickness reduction. Optionally, the grooves may be a channel, a
recess, or the like, or any combination thereof. The distance
between the grooves was selected such that alox 353 grown from each
groove overlaps with the alox grown area from a groove in the
adjacent row. Each groove has been filled during the anodization
process due to the growth of alox 353 outwards from the metal.
Substrate 350, including aluminum base 351 and alox 353 may be the
same or substantially similar to that shown in FIGS. 2A-2C at 200,
201, and 203.
[0094] FIG. 3G shows a substrate 360 including a section of an
aluminum base 361 with two strips of grown alox 363, following a
deep anodization process using grooves for thickness reduction.
Optionally, the grooves may be a channel, a recess, or the like, or
any combination thereof. Each strip of grown alox 363 was created
from a groove, the distance between the grooves selected such that
two strips of grown alox are separated by a portion of aluminum
base 361. Each groove has been filled during the anodization
process due to the growth of alox 363 outwards from the metal.
Substrate 360, including aluminum base 361 and alox 363, may be the
same or substantially similar to that shown in FIGS. 2A-2C at 200,
201 and 203.
[0095] FIG. 3H shows a substrate 370 including a section of an
aluminum base 371 with three strips of grown alox 373, following a
deep anodization process using grooves for thickness reduction.
Optionally, the grooves may be a channel, a recess, or the like, or
any combination thereof Each strip of grown alox 373 was created
from a groove, the distance between the grooves selected such that
three strips of grown alox are separated from one another by a
portion of aluminum base 371. Each groove has been filled during
the anodization process due to the growth of alox 373 outwards from
the metal. Substrate 370, including aluminum base 371 and alox 373,
may be the same or substantially similar to that shown in FIGS.
2A-2C at 200, 201 and 203.
[0096] Reference is made to FIGS. 4A-4E which schematically
illustrate several non-limiting, exemplary cross-sectional views of
thickness reduction configurations on a portion of a substrate,
prior to anodization; and to FIGS. 4A'-4E' which schematically
illustrate the same cross-sectional views of the portion following
deep anodization, in accordance with some embodiments of the
disclosure. The method illustrated comprises two-sided deep
anodization, and may optionally include one-sided deep anodization.
Thickness reduction by creating indentions may be performed by
using methods known in the art, such as, for example, chemical or
electrochemical or dry etching through an opening in a mask; jet
spraying of an etchant; or through mechanical means such as
milling, stamping, electro erosion, ultrasound cutting, laser
cutting, or any combination thereof. Anodization may be performed
using methods known in the art, for example, porous
anodization.
[0097] FIG. 4A shows a substrate 410, including a section of an
aluminum base 411 comprising a blind hole 412 created on one side
of the base, and a second blind hole 412' created on an opposite
side of the base, the holes substantially aligned such that one is
on top of the other. Following two-sided deep anodization,
cross-sectional view FIG. 4A' shows growth of alox 413 from blind
holes 412 and 412' into and out of base 411 in the areas of the
holes. Alox 413 overlaps to form an anodized section covering a
thickness of the base, over a portion of the section. Blind holes
412 and 412' have been filled during the anodization process due to
the growth of alox 413 outwards from the metal. Substrate 410,
including aluminum base 411, holes 412 and 412', and alox 413, may
be the same or substantially similar to that shown in FIGS. 1A-1C
and/or 2A-2C at 100, 101, 102, and 103, respectively.
[0098] FIG. 4B shows a substrate 420, including a section of an
aluminum base 421 comprising a series of blind holes 422 created on
one side of the base, and a second series of blind hole 422'
created on an opposite side of the base, the holes substantially
aligned such that one is on top of the other. Following two-sided
deep anodization, cross-sectional view FIG. 4B' shows growth of
alox 423 from blind holes 422 and 422' into and out of base 421 in
the areas of the holes. Alox 423 overlaps to form an anodized
section covering a thickness of the base over the whole section.
Blind holes 422 and 422' have been filled during the anodization
process due to the growth of alox 423 outwards from the metal.
Substrate 420, including aluminum base 421, hole 422 and 422', and
alox 423, may be the same or substantially similar to that shown in
FIGS. 1A-1C and/or 2A-2C at 100, 101, 102, and 103, respectively,
with the exception that blind holes 422 and 422' are rectangular
shaped.
[0099] FIG. 4C shows a substrate 430, including a section of an
aluminum base 431, comprising a series of blind holes 432 created
on one side of the base, and a second series of blind holes 432'
created on an opposite side of the base, the holes substantially
aligned such that one hole on one side is on top of a hole on the
other side. Following two-sided deep anodization, cross-sectional
view FIG. 4C' shows growth of alox 433 from blind holes 432 and
432' into and out of base 431 in the areas of the holes. Alox 433
overlaps to form an anodized section covering a thickness of the
base over the whole section. Blind holes 432 and 432' have been
filled during the anodization process due to the growth of alox 433
outwards from the metal. Substrate 430, including aluminum base
431, holes 432 and 432', and alox 433, may be the same or
substantially similar to that shown in FIGS. 1A-1C and/or 2A-2C at
100, 101, 102, and 103, respectively.
[0100] FIG. 4D shows a substrate 440, including a section of an
aluminum base 441, comprising a blind hole 442 created on one side
of the base, and two blind holes 442' created on an opposite side
of the base, the holes on one side non-aligned with respect to the
holes on the other side. Following two-sided deep anodization,
cross-sectional view FIG. 4D' shows growth of alox 443 from blind
holes 442 and 442' into and out of base 441 in the areas of the
holes. Alox 443 overlaps to form an anodized section covering a
thickness of the base, over a portion of the section comprised by
three blind holes 442 and 442'. Blind holes 442 and 442' have been
filled during the anodization process due to the growth of alox 443
outwards from the metal. Substrate 440, including aluminum base
441, holes 442 and 442', and alox 443, may be the same or
substantially similar to that shown in FIGS. 1A-1C and/or 2A-2C at
100, 101, 102, and 103, respectively.
[0101] FIG. 4E shows a substrate 450, including a section of an
aluminum base 451, comprising a series of blind holes 452 created
on one side of the base, and a second series of blind holes 452'
created on an opposite side of the base, the holes on one side
non-aligned with respect to the holes on the other side. Following
two-sided deep anodization, cross-sectional view FIG. 4E' shows
growth of alox 453 from blind holes 452 and 452' into and out of
base 451 in the areas of the holes. Alox 453 overlaps to form an
anodized section covering a thickness of the base over the whole
section. Blind holes 452 and 452' have been filled during the
anodization process due to the growth of alox 453 outwards from the
metal. Substrate 450, including aluminum base 451, holes 452 and
452', and alox 453, may be the same or substantially similar to
that shown in FIGS. 1A-1C and/or 2A-2C at 100, 101, 102, and 103,
respectively, with the exception that blind holes 452 and 452' are
rectangular shaped.
[0102] It should be clear to a person skilled in the art that there
are numerous alox configurations which may be created in substrates
using the described method, and that those shown above in the plan
views and/or cross-sectional views are not intended to be limiting
in any form or manner. Furthermore, there are numerous types,
quantities, and dimensions, of indentations which may be used,
including combination of types, and those shown (blind holes and/or
grooves) are not intended to be limiting in any way. Additionally,
the substrate may comprise any valve metal, the use of the aluminum
base (and alox) intended for exemplary purposes.
[0103] Reference is made to FIG. 5 which schematically illustrates
an exemplary thick ALOX.TM. substrate 500 following deep
anodization and comprising vertical isolated structures 503, in
accordance with some embodiments of the invention. Thick ALOX.TM.
substrate 500 is adapted to conduct heat from high power
dissipating electronic component 505 through aluminum via 501 to a
heat sink (not shown). In accordance with some embodiments of the
invention, a thickness of aluminum via 501 is at least 200 .mu.m.
Substrate 500 comprises a plurality of aluminum vias 501, the
aluminum sections electrically isolated from one another by
vertical isolated structures 503 which extend from one side of the
substrate to the other. In accordance with an embodiment of the
invention, substrate 500 was formed by a two-sided deep anodization
process comprising thickness reduction, vertical island structures
503 comprising alox grown according to the method disclosed
herein.
[0104] Reference is made to FIG. 6 which illustrates a flow diagram
of an exemplary method of performing deep anodization, in
accordance with an embodiment of the invention. For exemplary
purposes, reference is made to FIGS. 1A-1C and FIGS. 2A-2C. It may
be appreciated by a person skilled in the art that the method
described herein may be applied in other sequences for the
described embodiments, and may be applied in the same sequence
described, or in other sequences, to other embodiments of the
disclosure.
[STEP 601] Select an anodization process to be used in fabricating
substrate 100. [STEP 602] Determine the growth of alox 103 in and
out of metal base 101. For example, when using an anodization
process used to create an ALOX.TM. substrate, alox growth into
aluminum is approximately 70% while, out of the aluminum, growth is
approximately 30%. [STEP 603] Determine the type of indentation to
be created on the surface of the portion of base 101 to be
anodized, for example, blind holes 102. The size and depth of the
indentation is also determined. Optionally, the indentation may
comprise channels, grooves, recesses, and the like, or any
combination thereof. [STEP 604] Determine the position of the
indentation to be created on the surface of the portion of base 101
to be anodized. The position may be selected based on the decisions
made in the prior steps, and is intended to allow overlapping of
grown alox 103. [STEP 605] Create the indentation on the surface of
the portion of base 101 according to type and position. [STEP 606]
Perform deep anodization in indentations.
[0105] In the description and claims of embodiments of the present
invention, each of the words, "comprise" "include" and "have", and
forms thereof, are not necessarily limited to members in a list
with which the words may be associated.
[0106] The invention has been described using various detailed
descriptions of embodiments thereof that are provided by way of
example and are not intended to limit the scope of the invention.
The described embodiments may comprise different features, not all
of which are required in all embodiments of the invention. Some
embodiments of the invention utilize only some of the features or
possible combinations of the features. Variations of embodiments of
the invention that are described and embodiments of the invention
comprising different combinations of features noted in the
described embodiments will occur to persons with skill in the
art.
* * * * *